The present invention relates to a heating element, a seat heating unit, a seat, a steering wheel, as well as to various applications.
To heat seats, especially in passenger vehicles, primarily tin-plated or silver-coated copper conductors are utilized. Despite this coating, as a function of environmental conditions these heat conductors exhibit the formation of corrosion, which is induced by moisture and the influence of salts. Due to this formation of corrosion, the heat conductors experience damaging reductions in cross-sectional areas, followed by localized overheating and finally to a breakage of the heat conductor, which results in a shortened service life of the heat conductor. Furthermore, the coating with silver or tin, or also other metals, increases the friction between the individual filaments of the heat conductor to such an extent that due to its increased rigidity, the heat conductor can become bent or broken, and thus can be severely damaged. A further drawback of a metallic coating of the individual heat conductor filaments is the greatly differing redox potential of the coating metals relative to the actual material of the wire. Where the coating is not free of pores, and gaps or defect areas are present, corrosion occurs under the influence of electrolytes formed of water and salt, and hence a dissolving or decomposition of the base metal, which in turn represents damage to the heat conductor. Finally, the mechanical requirements of such conductors in seats are very high, which in many cases cannot be satisfactorily realized.
DE 38 32 342 C1 discloses a coated wire having a surface of platinum that encases a core of an alloy of 1 to 5% by weight tungsten, with the remainder being platinum. This coated wire is preferably used as a lead wire for a resistance thermometer having a precision resistor of platinum.
DE 31 25 980 A1 discloses a wire-like semi-finished product for an electrical conductor wire having a specific maximum diameter that at least in the region of its free outer surface is comprised essentially of platinum, whereby the surface is coated with a gold coating, and whereby the core of the conductor wire can be comprised of nickel.
A drawback of such a product, among others, is the use of difficult to work materials as well as their high cost.
It is therefore an object of the present invention to provide an electrical heating element that avoids the aforementioned drawbacks, especially a heating element that can withstand the high mechanical stresses of an electrical heating unit in a seat, especially in a seat of a motor vehicle, and which at the same time has an outstanding electrical conductivity paired with a low susceptibility to corrosion and relatively low manufacturing costs.